Duergar

From Monster Manual: The tyrannical duergar, also known as gray dwarves, dwell in fantastic cities deep in the Underdark. Using ancient dwarven knowledge and myriad slaves, they work tirelessly to expand their subterranean kingdoms. Most duergar (including females) are bald and have ashen gray skin. They wear drab clothing designed to blend in with stone, along with simple jewelry that reflects their severe and utilitarian demeanor.